A piece of granite fell on the worker, and he went into cardiac arrest before being revived by paramedics and taken to Stroger Hospital in serious condition for treatment, said Fire Department spokesman Will Knight.

The worker, who Hlepas said was alone at the time of the accident, appeared to have been moving stone slabs when several of them fell on him, a customer who was at the business at the time of the accident told the Tribune.

No one saw what happened to the worker, who has been with the company for about five years, Hlepas said. Others in the business came upon the injured man after they heard a loud noise and went to investigate, Hlepas said. The accident happened in a warehouse adjacent to the main building.

Chicago authorities and the U.S. Occupational Safety and Health Administration were investigating and had interviewed eight or nine people at the scene, Hlepas said.